In electrical utility underground residential wiring, common practice uses transformers supplied with secondary voltage bushings that include insulators with threaded studs. The threaded studs are provided to energize service and distribution cables through electrical connectors designed for assembly to them.
Where a multiplicity of cables are to be energized by the studs, a standard rectangular bar connector, machined on one end to provide a threaded borehole for assembly to the threaded stud, and providing electrical connections in the desired number, is commonly used.
Two types of connections are normally made to the secondary bushing stud. The first type is a threaded fit, wherein the connector is machined on one end to provide a threaded borehole with the same threading as the transformer stud. During assembly, the bar connector is threaded onto the stud and locked in position by a lock nut.
The other normal type of connection made to secondary bushing studs allows for the installation and the removal of the bar connector from the stud without disassembly of installed cables. The bar connector has a larger diameter threaded hole than the secondary bushing stud. However, the pitch of the threads in the bar connector is identical to that of the stud. This identical threading provides areas of inter-thread contact for current transfer from the stud to the connector. The bar is positioned on the stud and secured with a set screw.
Connectors used in residential underground construction are normally insulated. In some applications, where flooding of the transformer enclosure is common, water-tight connector assemblies are required.
A more common requirement in the above environment is that connections be insulated only to protect the lineman in wiring to the transformer initially and during subsequent maintenance. This arrangement is commonly described as dead front construction.
While some transformers have two adjacent studs, they are more normally provided with three angularly aligned bushings and associated studs. Due to space limitations, it is desirable to place the bar connector on the stud so that the wrench will have access to the set screws on the side of each bushing which presents the greatest clearance for the lineman. This is referred to as right- and left-hand installation.
The insulator of the present invention is used with and satisfies all of the requirements for dead front construction while introducing new features that convenience assembly, allow for visual inspection of connections after assembly, reduce installing time, and promote safety.
Further objects of the invention include
1. An insulator cover for a transformer bar connector which is configured to prevent brush contacts.
2. An insulator cover which includes common access ports for both cable installation and for the tightening of the set screws.
3. An insulator cover which includes access ports and means therein for temporarily restraining the cables in a fixed position during visual inspection prior to the securing of the set screws.
4. An insulator cover including access ports having retaining means for restraining tools, such as a wrench, being used for tightening the set screws so that if the wrench is released it will not drop free.
5. An insulator cover which has at least two access ports spaced 90.degree. from each other so as to provide for right- and left-hand installation.
6. An insulator cover for providing dead front protection on existing bare connector installations irrespective of cable outlet spacing.
These and other objects of the invention will become apparent from the following discussion taken together with the drawings.